This proposal contains plans for a detailed biochemical study of eukaryotic tRNA gene expression and its control. Using cloned yeast tRNA genes the work will focus on the mechanism of their transcription and the characterization of the components of the transcription complex. Some of the enzymes involved in the conversion of the tRNA precursors to mature tRNA (e.g., RNase P, splicing endonuclease, tRNA modifying enzymes) will be cloned, purified and studied. The analysis of nonsense suppressor mutants of yeast will corroborate the biochemical results of this study.